A suspension thrust bearing conventionally comprises a rolling bearing forming an axial thrust bearing and comprising an upper ring and a lower ring between which is disposed a row of rolling elements, for example balls or rollers. An oblique contact bearing is preferably used to withstand both radial and axial forces exerted on the suspension thrust bearing device. The upper and lower rings are usually mounted in contact with upper or lower cover supporting or bearing parts such as cups or covers. The upper and lower covers form a housing for the bearing rings and provide an interface between said rings and the neighbouring elements.
Such a suspension thrust bearing device is disposed on the upper portion of the suspension strut between a suspension spring and a upper member fastened to the chassis of the vehicle. The suspension spring is fitted around a damper piston rod, the end of which may be fastened to the chassis of the vehicle via an elastic block for filtering vibrations. The suspension spring, which is generally a coil spring, axially bears, directly or indirectly, on the lower bearing cover of the suspension thrust bearing device. The upper cover is fixed to the chassis of the vehicle.
The suspension thrust bearing thus enables transmission of axial forces between the suspension spring and the chassis of the vehicle while allowing a relative angular movement between the lower cover, which is mobile in rotation, and the elastic filter block. This angular movement occurs when the steered wheels of the vehicle are turned and/or when the suspension spring is compressed.
The inside of the rolling bearing, i.e. the space between the two rings, contains a lubricant. For the correct operation of the rolling bearing, it is necessary to retain the lubricant inside the rolling bearing and at the same time to prevent the penetration of solid or liquid pollutants into the inside of the rolling bearing. To this end, seals may be disposed at the junction between the two rings or shaped in such a manner as to form a labyrinth seal.
Referenced can be made to the French patent application 2 901 737 (SKF), which describes a suspension thrust bearing device including a lower supporting cover and a bearing mounted so as to bear on it. The lower supporting cover is made from a synthetic material and is associated with an element for filtering vibrations provided with a stiffener armature. This results in a good distribution of the load applied by the suspension spring and vibrations are significantly reduced. In operation, a suspension thrust bearing device of this kind is exposed to water splashes. To this end the upper and lower supporting covers are conformed to produce a contactless seal by means of a labyrinth seal both on the inner side and on the outer side, which is more exposed to water splashes. The above earlier patent application also provides attachment means between the upper cover and the lower cover to prevent separation of the two covers before mounting the suspension thrust bearing.
French patent application 2 928 187 (SKF) describes another embodiment of a suspension thrust bearing in which the lower cover has a body formed of a rigid synthetic material to transmit axial forces between the spring and the bearing and a flexible synthetic material that has sealing lips that may come into contact with axial cylindrical skirts forming part of the upper cover. In the above document, axial retention of the upper cover relative to the lower cover is achieved by cooperation between two hooks provided on the upper cover and a flexible sealing lip, which thus has two different technical functions. Having two functions may lead to drawbacks. To provide a suitable seal, the sealing lip must be as flexible as possible. This flexibility may compromise good axial retention of the upper cover relative to the lower cover.
The aim of the invention is to overcome the drawbacks of the prior art.